Measurement of the 99Tc β spectrum with Silicon Drift Detectors
Abstract
The need for reliable calculations of Nuclear Matrix Elements is compelling for the next generation of neutrinoless double-beta decay experiments. This requires nuclear models to be validated against experimental data, such as non-unique forbidden β decays, which have been found sensitive to details in nuclear calculations, most importantly to the renormalization of the axial and vector currents. %, parametrized as a quenching of gA and gV. We report here a measurement of the 2nd forbidden 99Tc β spectrum performed for the first time with Silicon Drift Detectors, state-of-the-art semiconductor detectors for low-energy spectroscopy. We designed a novel hybrid spectrometer using a LYSO crystal read by a SiPM to precisely calibrate our main detector and to accurately measure the background. We then compared our measured spectrum with one obtained using cryogenic calorimeters, as well as with predictions from the Realistic Shell Model. Starting from Realistic Shell Model calculations performed with Bare decay operators, we carried out a Bayesian analysis to extract the average quenching factors required to reproduce both the measured spectral shape and the experimental half-life, obtaining qgA=0.40(1) and qgV=0.47(1). These values quantify the average renormalization of the axial and vector currents, respectively, and were compared with those predicted by RSM calculations employing Effective decay operators, thereby providing a benchmark for assessing the ability of the model to describe the second-forbidden β decay of 99Tc. More broadly, this comparison tests the reliability of the theoretical framework also used to predict 0νββ nuclear matrix elements.
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BibTeX
@misc{nava2026measurement,
title = {{Measurement of the $^99$Tc $β$ spectrum with Silicon Drift Detectors}},
author = {Andrea Nava and Andrea Del Contrasto and Leonardo Bernardini and Matteo Biassoni and Tommaso Bradanini and Chiara Brofferio and Marco Carminati and Silvia Capelli and Francesco Cappuzzello and Manuela Cavallaro and Massimiliano Clemenza and Giovanni De Gregorio and Giulio Gagliardi and Giorgio Grosso and Nunzio Itaco and Irene Nutini and Alessia Pozzi and Nicola Zorzi},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.05640},
eprint = {2609.05640},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.05640},
}
RIS
TY - UNPB
TI - Measurement of the ^99Tc β spectrum with Silicon Drift Detectors
AU - Andrea Nava
AU - Andrea Del Contrasto
AU - Leonardo Bernardini
AU - Matteo Biassoni
AU - Tommaso Bradanini
AU - Chiara Brofferio
AU - Marco Carminati
AU - Silvia Capelli
AU - Francesco Cappuzzello
AU - Manuela Cavallaro
AU - Massimiliano Clemenza
AU - Giovanni De Gregorio
AU - Giulio Gagliardi
AU - Giorgio Grosso
AU - Nunzio Itaco
AU - Irene Nutini
AU - Alessia Pozzi
AU - Nicola Zorzi
PY - 2026
DA - 2026/09/04
PB - arXiv
DO - 10.48550/arxiv.2609.05640
UR - https://arxiv.org/abs/2609.05640
AB - The need for reliable calculations of Nuclear Matrix Elements is compelling for the next generation of neutrinoless double-beta decay experiments. This requires nuclear models to be validated against experimental data, such as non-unique forbidden β decays, which have been found sensitive to details in nuclear calculations, most importantly to the renormalization of the axial and vector currents. %, parametrized as a quenching of g_A and g_V. We report here a measurement of the 2^nd forbidden ^99Tc β spectrum performed for the first time with Silicon Drift Detectors, state-of-the-art semiconductor detectors for low-energy spectroscopy. We designed a novel hybrid spectrometer using a LYSO crystal read by a SiPM to precisely calibrate our main detector and to accurately measure the background. We then compared our measured spectrum with one obtained using cryogenic calorimeters, as well as with predictions from the Realistic Shell Model. Starting from Realistic Shell Model calculations performed with Bare decay operators, we carried out a Bayesian analysis to extract the average quenching factors required to reproduce both the measured spectral shape and the experimental half-life, obtaining q_g_A=0.40(1) and q_g_V=0.47(1). These values quantify the average renormalization of the axial and vector currents, respectively, and were compared with those predicted by RSM calculations employing Effective decay operators, thereby providing a benchmark for assessing the ability of the model to describe the second-forbidden β decay of ^99Tc. More broadly, this comparison tests the reliability of the theoretical framework also used to predict 0νββ nuclear matrix elements.
ER -